The subject matter of the present invention relates to well logging tools, and in particular, to a sonic isolation joint for a sonic well logging tool.
Well logging tools are used in boreholes of oil wells for the purpose of determining if oil exists in a formation of the borehole. Some well logging tools are sonic in nature, in that they transmit a sonic pressure wave into the formation and receive the sonic pressure wave from the formation. The received sonic pressure wave is analyzed for the purpose of determining if oil exists in the formation. When the sonic pressure wave is transmitted, a corresponding compressional and flexural vibrational wave is transmitted longitudinally along the sonic tool, from the transmitter to the receiver. These compressional and flexural waves interfere with the performance of the sonic receiver. The receiver will record certain received sonic signals. Due to the existence of the compressional and flexural waves, it is difficult to determine which part of the received sonic signals corresponds to compressional/flexural waves, and which part corresponds to sonic pressure waves from the formation. Therefore, in order to improve the performance of the sonic well logging tool receiver, an attenuation member is placed intermediate the sonic transmitter and the sonic receiver. The attenuation member is designed to attenuate the compressional and flexural wave transmitted longitudinally along the sonic well logging tool. However, the weight of modern day well logging tools is increasing, due to the increased length of the well logging tool string. As a result, a new attenuation member design is needed to properly provide the necessary degree of compressional and flexural wave attenuation while, at the same time, withstanding the weight of the sonic well logging tool string.